Solar and Stellar Astrophysics
Serendipitous Discovery of a Faint Planetary Nebula in the Massive Young LMC Cluster NGC 1866
Howard E. Bond, Nate Bastian, Andrea Bellini et al. (+5 more)
During an integral-field spectroscopic study of
stars in the massive young open cluster NGC 1866 in the Large Magellanic Cloud, we serendipitously discovered a faint planetary nebula (PN). We designate it "Ka LMC 1," and find that its location near the cluster center, along with the agreement of its radial velocity with that of the cluster, imply a high probability of membership in NGC 1866. The 200 Myr age of the cluster indicates that the PN's progenitor
star had an initial mass of about 3.9 Msun. The integrated spectrum of Ka LMC 1 shows strong emission lines of [N II], consistent with it being a "Type I" nitrogen-rich PN. The nebula exhibits a classical ring morphology, with a diameter of ~6", corresponding to an advanced expansion age of about 18,000 yr. Archival images of NGC 1866 obtained with the Hubble Space
Telescope reveal a faint blue central
star. Comparison of the
star's luminosity with predictions from one set of theoretical post-asymptotic-
giant-branch evolutionary tracks for single
stars implies an age roughly consistent with the dynamical age of the PN, but the agreement with alternative modern tracks is much poorer. Analysis of the emission-line spectrum suggests considerable
dust extinction within the nebula; however the central
star possibly suffers little reddening because we may be viewing it nearly pole-on in a bipolar PN. Our accidental discovery was made using data that are not ideal for study of Ka LMC 1; we suggest several avenues of future targeted studies that would provide valuable and nearly unique new information for constraining models of late
stellar evolution.
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All authors Howard E. Bond, Nate Bastian, Andrea Bellini, Sebastian Kamann, Mattia Libralato, Florian Niederhofer, Martin M. Roth, Azlizan A. Soemitro
High Energy Astrophysical Phenomena
TRAPUM search for pulsars in supernova remnants and pulsar wind nebulae - II. Survey analysis and population study
J. D. Turner, B. W. Stappers, E. Barr et al. (+16 more)
We present the second and final set of TRAPUM searches for
pulsars at 1284 MHz inside
supernova remnants and
pulsar wind nebulae with the MeerKAT
telescope. No new
pulsars were detected for any of the 80 targets, which include some unidentified TeV sources that could be
pulsar wind nebulae. The mean upper limit on the flux density of undetected
pulsars is 52 $\mu$Jy, which includes the average sensitivity loss across the coherent beam tiling pattern. This survey is the largest and most sensitive multi-target campaign of its kind. We explore the selection effects that precluded discoveries by testing the parameters of the survey iteratively against many simulated populations of young
pulsars in
supernova remnants. For the synthetic
pulsars that were undetected, we find evidence that, after beaming effects are accounted for, about 45 per cent of
pulsars are too faint, 30 per cent are too smeared by scattering, and a further 25 per cent have a modelled projected location which places them outside their
supernova remnant. The simulations are repeated for the S1 subband of the MeerKAT S-band receivers, resulting in a 50-150 per cent increase in the number of discoveries compared to L-band depending on the flux density limit achieved. Therefore, higher frequency searches that can also achieve improved flux density limits are the best hope for future targeted searches. We also report updated properties for the two previous discoveries, including a polarimetry study of PSR J1831$-$0941 finding a rotation measure of 401$\pm$1 rad m$^2$.
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All authors J. D. Turner, B. W. Stappers, E. Barr, M. Burgay, M. Colom i Bernadich, V. Graber, M. J. Keith, M. Kramer, L. Levin, Y. P. Men, C. Pardo-Araujo, T. Thongmeearkom, J. Tian, P. V. Padmanabh, P. Weltevrede, J. Behrend, W. Chen, E. F. Keane, A. Ridolfi
Instrumentation and Methods for Astrophysics
Readout of Microwave Kinetic Inductance Detector (MKID) Arrays for Habitable Worlds Observatory Using a Polyphase Filterbank Algorithm
Oketa Basha, Tracee Lynn Jamison-Hooks, Philip Mauskopf et al. (+12 more)
The Habitable Worlds Observatory (HWO), a nextgeneration ultraviolet/optical/infrared space
telescope, will require detector technologies capable of supporting substantially larger pixel-count arrays than those flown on previous missions. Microwave Kinetic Inductance Detectors (MKIDs) provide a scalable solution through microwave multiplexing and have already been demonstrated in balloon-borne instruments using Field-Programmable Gate Arrays (FPGAs) for real-time signal processing. A central element of MKID readout is the Polyphase Filter Bank (PFB) spectrometer, which converts digitized timedomain signals into finely resolved frequency channels for subsequent analysis. To meet the demands for broader bandwidths and higher spectral resolution driven by emerging science goals, efficient FPGA-based implementations of the PFB are essential. This work presents current results from a fixed-point digital design methodology for deploying the PFB architecture on spacequalified FPGAs. The approach emphasizes efficient resource utilization and numerical precision while satisfying stringent performance constraints, enabling scalable, high-resolution spectral processing for future space observatories and remote sensing applications.
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All authors Oketa Basha, Tracee Lynn Jamison-Hooks, Philip Mauskopf, Lynn Miles, Sanetra Newman-Bailey, Abarna Karthikeyan, Mohammad Samad, Mariya Taylor, Sarah E. Kay, Sean Bryan, Devika Band, Thomas Essinger-Hileman, Sumit Dahal, Adrian Sinclair, Caleb Distel
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Structure formation in a non-canonical scalar field model of clustering dark energy
Zanyar Ebrahimi and Kayoomars Karami
This paper examines the growth of dark matter and dark energy perturbations within a non-canonical scalar field model characterized by an exponential potential. Through dynamical system analysis, we identify critical points and track the background
evolution of a spatially flat FLRW universe dominated by dark energy and pressureless dark matter. We systematically derive key cosmological quantities, including the Hubble parameter, deceleration parameter, density parameters, and the scalar field's equation of state, and explore their dependence on model parameters. Within the linear perturbation framework, employing the pseudo-Newtonian formalism, we compute the growth factor of matter density perturbations. To investigate the non-linear regime of structure formation, we employ the spherical collapse model and derive its key parameters. Building on these findings, we compute the function $f(z)\sigma_8(z)$ and the relative number density of
halo objects exceeding a given mass threshold. Our results indicate that non-canonical scalar field models can effectively account for both background
cosmic evolution and the growth of structure, offering potential insights into observational constraints and large-scale dynamics.
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High Energy Astrophysical Phenomena
Association of the IceCube neutrinos with CAZ blazar light curves
Pouya M. Kouch, Talvikki Hovatta, Elina Lindfors et al. (+3 more)
The IceCube
Neutrino Observatory has detected several hundred high-energy
neutrinos from
cosmic sources. Despite numerous studies searching for their origin, it is still not known which sources emit them. A few likely individual associations exist with active
galactic nuclei (AGNs), mostly comprising blazars (AGNs with jets pointed toward Earth). Nonetheless, on a population level, blazar-
neutrino correlation strengths are rather weak. This could mean that blazars as a population do not emit high-energy
neutrinos or that the detection power of the tests is insufficient due to the strong atmospheric
neutrino background. By assuming an increase in high-energy
neutrino emission during major blazar
flares, in our previous studies, we leveraged the
neutrino arrival time to boost the detection power. Here, we utilize the same principle, while substantially increasing the number of blazars in the sample. We searched for the spatiotemporal correlation of 356 IceCube high-energy
neutrinos with major optical
flares of 3225
radio- and 3814 $\gamma$-ray-selected blazars. We found that despite the increase in data size, the number of likely spatiotemporal associations remained low and the overall correlation strengths weak. Two individual associations were shown to drive our strongest correlation, namely, the only $>$2$\sigma$ post-trial spatiotemporal correlation, occurring with the BL Lac objects of the
radio-selected blazar sample. We estimated that $\lesssim$8% of the detected
cosmic neutrinos were emitted by blazars during major optical
flares. As a complementary analysis, we compared the synchrotron peak frequency,
redshift, Doppler factor, X-ray brightness, and optical variability of spatially
neutrino-associated blazars to those of the general blazar population. We found that spatially
neutrino-associated blazars have a Doppler factor and X-ray brightness that are higher than average.
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All authors Pouya M. Kouch, Talvikki Hovatta, Elina Lindfors, Ioannis Liodakis, Karri I.I. Koljonen, Alessandro Paggi
High Energy Astrophysical Phenomena
CAZ catalog and optical light curves of 7918 blazar-selected active galactic nuclei
Pouya M. Kouch, Elina Lindfors, Talvikki Hovatta et al. (+10 more)
Active
galactic nuclei (AGN) are some of the brightest and most variable objects in the Universe. Those with relativistic jets observed at small viewing angles are blazars. Due to Doppler boosting, blazars exhibit extreme
stochastic variability. While the origin of this variability is thought to be changes in the
accretion flow and jet dynamics, much about blazar variability remains unknown. In this paper we use several blazar-dominated AGN samples to form a catalog of 7918 blazars and candidates – the largest to date. We also collected source types,
redshifts, peak frequencies of the spectral energy distribution,
radio variability Doppler factors, and X-ray flux densities for as many sources as possible. We used all-sky surveys (CRTS, ATLAS, and ZTF, abbreviated as “CAZ”) to extract their optical multiband flux density on a nightly basis between 2007 and 2023, and we constructed as long and as high cadence light curves as possible for as many sources as attainable. We quantified the variability of the light curves and applied the
Bayesian blocks
algorithm to determine their flaring periods. The CAZ catalog and light curves as well as the corresponding
Bayesian blocks and flaring periods are all provided in the accompanying electronic tables, with the goal of enabling analyses involving jetted AGN variability with unprecedented sample sizes. Overall, we find (1) optical
flares generally have a faster rise than decay; (2) optical brightness and variability are strongly dependent on the synchrotron peak frequency; (3) flat spectrum
radio quasars and BL Lac objects have comparable optical variability and
flare characteristics at the same synchrotron peak frequency; and (4) optical
flare times tend to decrease while amplitudes increase with an increasing
radio variability Doppler factor.
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All authors Pouya M. Kouch, Elina Lindfors, Talvikki Hovatta, Ioannis Liodakis, Karri I.I. Koljonen, Alessandro Paggi, Kari Nilsson, Jenni Jormanainen, Vandad Fallah Ramazani, Sofia Kankkunen, Folkert Wierda, Sarah M. Wagner, Matthew J. Graham
Cosmology and Nongalactic Astrophysics
The Manticore-Local Cluster Catalogue: A Posterior Map of Massive Structures in the Nearby Universe
Stuart McAlpine
We present a publicly available catalogue of massive structures in the nearby Universe, constructed from the Manticore-Local posterior ensemble, a
Bayesian field-level reconstruction that infers the underlying dark matter distribution from 2M++
galaxies. We identify massive structures by clustering the central
haloes inferred at z = 0 across the 80 posterior realizations, selecting at most one member per realization. These associations serve as probabilistic counterparts to individual massive clusters, each with robust posterior estimates of mass, position, and velocity. The fiducial catalogue contains 401 associations with ambiguity rates below 5%, and at least 20 member
haloes across the posterior ensemble. We independently validate these systems through stacked Planck thermal SZ measurements, which yield significant detections showing the expected mass trend, consistent with the established Y–M scaling relation. Many associations exhibit coherent evolutionary histories, meaning that their progenitor
haloes across the posterior ensemble trace consistent merger pathways rather than diverging into unrelated assembly scenarios. Even with only z = 0 constraints, the inference narrows each system's possible assembly pathway: progenitor
haloes at earlier times occupy Lagrangian volumes 2–5 times smaller than those of mass-matched
haloes in unconstrained LCDM simulations, reflecting genuine information gain from the observational constraints. Cross-matches with X-ray catalogues reveal systematic mass-scale differences that align with known observational biases: Manticore-Local masses are typically 1.7 times ROSAT-based estimates but agree at unity with weak-
lensing-calibrated eROSITA measurements. This illustrates the catalogue's potential to flag individual systems with significant mass discrepancies for targeted investigation.
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Earth and Planetary Astrophysics
Deuteration of water in protoplanetary discs during luminosity outbursts: model predictions for FU Ori discs
Anastasiia Topchieva, Tamara Molyarova and Anton Vasyunin
Luminosity outbursts of FU Ori-type objects (FUors) allow us to observe in the gas the molecules that are typically present in the ice in protoplanetary discs. In particular, the fraction of deuterated water, which is usually is mostly frozen in the midplane of a protoplanetary disc, has been measured for the first time in the gas of the disc around a FUor V883 Ori. We test the hypothesis that the observed high HDO/H$_{2}$O ratio in the V883 Ori protoplanetary disc can be explained by luminosity outbursts of different amplitude, including a series of two consecutive outbursts. Using the ANDES astrochemical code, we modelled the distributions of water and deuterated water abundances under the action of luminosity outbursts of different amplitudes (from 400 to 10 000 $L_{\odot}$) and at different
stellar luminosities at the pre-outburst stage. We show that the best agreement with the observed HDO/H$_{2}$O profile is obtained for outburst amplitudes of 2 000 and 10 000 $L_{\odot}$, while the observed bolometric luminosity of V883 Ori does not exceed 400 $L_{\odot}$. We discuss possible reasons for this discrepancy, including the presence of past luminosity outbursts, the age of the
star, and the influence of additional heating mechanisms in the midplane of the protoplanetary disc. We also consider how the high observed $\rm HDO/H_{2}O$ ratio may be related to the
evolution of the chemical composition of the ice in the protoplanetary disc and the chemical processes activated under outburst conditions.
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Astrophysics of Galaxies
XRISM-Subaru views of Abell 754: Energetic ICM Motions Revealed by XRISM/Resolve
Yuki Omiya, Nobuhiro Okabe, Kazuhiro Nakazawa et al. (+4 more)
We present high-resolution X-ray spectroscopy of the merging cluster Abell~754 using XRISM/Resolve. In GO1 phase, XRISM/Resolve observed Abell 754 in two deep pointings, targeting the eastern primary core (114~ks) and the middle of the X-ray filamentary structure (190~ks). Spectral fits to full field-of-view data reveal a line-of-sight velocity difference of $656 \pm 35$~km~s$^{-1}$ between the two pointing, corresponding to a bulk Mach number of 0.45$\pm$0.03. Velocity dispersions are measured to be $220^{+26}_{-29}$~km~s$^{-1}$ and $279^{+24}_{-23}$~km~s$^{-1}$ in the eastern and middle pointing, respectively. Within the eastern core, the velocity dispersion shows spatial variation, reaching $497^{+144}_{-117}$~km~s$^{-1}$ in the southern core with high temperature – among the largest values yet reported in
galaxy clusters to date. Narrow-band analysis of the Fe-K complex in this region reveals systematically higher temperatures derived from He-like and H-like Fe line ratio compared to those obtained via broadband fits, indicating multi-phase structures. Two-temperature modeling further separates a cooler core phase from a hotter, shock or
turbulence-heated phase whose velocity is blueshifted, similar to that of the middle pointing. These results point to a mixing interface where post-shock gas from the south overlaps, in projection, with cooler core gas, inflating the observed line widths in this region. Weak-
lensing analysis with Subaru/HSC and Suprime-cam confirms that the eastern component is about twice as massive as the western one, consistent with disruption and gas stripping of the latter. The curved morphology of the eastern X-ray core, together with the measured kinematics, is naturally explained by an off-axis, post–core-passage merger that imparts angular momentum and drives large-scale rotational and fallback flows.
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All authors Yuki Omiya, Nobuhiro Okabe, Kazuhiro Nakazawa, Naomi Ota, Yuto Ichinohe, Shutaro Ueda, Nhan T. Nguyen-dang
Astrophysics of Galaxies
How Fast Could Supermassive Black Holes Grow At the Epoch of Reionization?
Ziyong Wu, Renyue Cen and Romain Teyssier
Utilizing cosmological hydrodynamic simulations we show that there is a brief super-Eddington
accretion phase in typical
halos at high
redshift, impervious to AGN self-regulation. However, once having attained a black hole mass of $10^4-10^5\msun$, AGN feedback process can self-regulate to guide the SMBHs to grow at a significantly slower, sub-Eddington rate. By
redshift $z\sim 10$ the black hole mass with an initial super-Eddington jump-start is caught up by that in the case with a steady Eddington limited case. Thus a continuous Eddington limit case represents the fastest possible route to maximally grow SMBHs. To account for the observed $z=7-10$
quasars with supermassive black holes of billions of
solar masses, our analysis establishes firmer ground for the need of seed masses of $10^4-10^5\msun$ that are not grown via an earlier super-Eddington phase.
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High Energy Astrophysical Phenomena
A UV to X-Ray View of Soft Excess in Type 1 Active Galactic Nuclei. II. Broadband Correlations
Shi-Jiang Chen, Jun-Xian Wang, Jia-Lai Kang et al. (+5 more)
The physical origin of soft X-ray excess (SE) is a long lasting question, with two prevailing theories – “warm corona” and “ionized reflection” – dominating the discussion. In the warm corona scenario, SE originates from upscattered disk
photons and should therefore correlate strongly with UV emission. Conversely, in the ionized reflection scenario, SE arises from the illumination of the
accretion disk by the hot corona and should primarily correlate with the hard X-ray primary continuum (PC). In this second paper of the series, we investigate the correlations among SE, UV and PC, leveraging a sample of 59 unobscured type 1 AGNs compiled in \citet{Chen+2025a}. Our extensive analysis reveals a strong intrinsic correlation between SE and UV that remains robust after controlling for PC ($p_\mathrm{null}\lesssim 10^{-7}$). In contrast, the correlation between SE and PC is weaker but still statistically significant ($p_\mathrm{null}\lesssim 5\times 10^{-2}$). These findings suggest that, in addition to ionized reflection – a natural outcome of the hot corona illuminating the disk – a warm corona component is essential, and may even dominate, in producing the soft excess. Additionally, we report a mild anti-correlation between SE strength ($q$) and PC
photon index ($\Gamma_\mathrm{PC}$) ($p_\mathrm{null}=10^{-2}$), suggesting a potential competition between the warm and hot coronae. Finally, we find that the $\Gamma_\mathrm{PC}$ values we derived with SE properly incorporated exhibit a much weaker correlation with $\lambda_\mathrm{Edd}$ ($p_\mathrm{null}=2\times 10^{-2}$) than previously reported in the literature. This highlights the critical role of accurately modeling SE in studies of the $\Gamma_\mathrm{PC}$–$\lambda_\mathrm{Edd}$ relation.
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All authors Shi-Jiang Chen, Jun-Xian Wang, Jia-Lai Kang, Wen-Yong Kang, Hao Sou, Teng Liu, Zhen-Yi Cai, Zhen-Bo Su
Astrophysics of Galaxies · Cross-listed from gr-qc
The deep-MOND limit – a study in Primary vs secondary predictions
Mordehai Milgrom
In default of a fundamental MOND theory – a FUNDAMOND – I advocate that, alongside searching for one, we should try to identify predictions that follow from wide classes of MOND theories, if not necessarily from all. In particular, predictions that follow from only the basic tenets of MOND – “primary predictions” – are shared by all MOND theories, and are especially valuable. Such predictions permit us to test the MOND paradigm itself, or at least large parts of it, without yet having a FUNDAMOND. Concentrating on the deep-MOND limit, I discuss examples of either type of predictions. For some examples of primary predictions, I demonstrate how they follow from the basic tenets (which I first formulate). I emphasize that even predictions that pertain to the deep-MOND limit - namely, those that concern gravitating systems that have low accelerations everywhere – require the full set of MOND tenets, including the existence of a Newtonian limit close to the deep-MOND regime. This is because Newtonian dynamics is a unique theory that all MOND theories must tend to in the limit of high accelerations, and it strongly constrains aspects of the deep-MOND regime, if the transition between the limits is fast enough, which is one of the MOND tenets.
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High Energy Astrophysical Phenomena
Implications of Joint Spectral Analysis of Gamma-Ray Bursts detected by Fermi Large Area Telescope and Gamma-ray Burst Monitor on Phenomenological Correlations
T. K. M. Aldowma, S. Razzaque, R. Martinelli et al. (+6 more)
Gamma-ray bursts (GRBs) have emerged as powerful cosmological probes for exploring the distant Universe, owing to their immense luminosities and detectability at high
redshifts. Several empirical correlations have been established, particularly involving their energy properties. This work aims to enhance the precision of these correlations through joint spectral analysis, focusing on reducing uncertainties in both the spectral indices and the peak energy ($E_{\rm p}$) derived from spectral fitting. We extend previous studies using both traditional and novel spectral models, utilizing a sample of 37 GRBs observed by the
Fermi Gamma-ray Burst Monitor (GBM) and Large Area
Telescope (LAT), incorporating the LAT Low-Energy (LLE) technique, over the period 2008-2024. Our analysis compares results from joint fits (GBM-LAT-LLE) against those from GBM-only fits. The study focuses on fitting time-integrated ${\rm T}_{90}$ and peak flux in the rest frame. Among the observable phenomenological correlations, we revisit the Amati and Yonetoku relations: the Amati relation links the intrinsic peak energy ($E_{i,\rm p}$) to the total isotropic energy ($E_{\rm iso}$) emitted during ${\rm T}_{90}$, while the Yonetoku relation connects $E_{i,\rm p}$ to the isotropic luminosity ($L_{\rm iso}$). Refining these correlations aims to deepen our understanding of GRB energetics and improve the precision of cosmological parameter estimates derived from GRB observations.
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All authors T. K. M. Aldowma, S. Razzaque, R. Martinelli, R. Gupta, F. Longo, N. Omodei, N. Di Lalla, J. L. Racusin, A. H. Airasca
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Constraining Black Hole Shadows in Dunkl Spacetime using CUDA Numerical Computations
Saad Eddine Baddis, Adil Belhaj, Hajar Belmahi et al. (+1 more)
With the help of CUDA high-performance numerical codes exploited in machine learning, we investigate the shadow aspect of new rotating and charged black holes using the Dunkl derivative formalism. Precisely, we first establish the corresponding metric function encoding the involved physical properties including the optical character. Exploiting such accelerated simulations, we approach the horizon radius behaviors in order to determine the regions of the module space providing physical solutions. Applying the Hamilton-Jacobi mechanism, we assess the shadow aspect for non-rotating and rotating solutions. Using such an aspect, we evaluate the energy rate of emission. Developing a high-performance CUDA numerical code, we derive strict constraints on the Dunkl deformation parameters in order to establish a link with the shadow observations provided by the Event Horizon
Telescope collaboration.
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All authors Saad Eddine Baddis, Adil Belhaj, Hajar Belmahi, Maryem Jemri
Astrophysics of Galaxies
CO in MASsive Spirals (CO-MASS): an IRAM 30m CO emission line survey of the CGM-MASS sample
Yu Huang, Jiangtao Li, Yan Jiang et al. (+4 more)
There exist extremely massive spiral
galaxies in isolated environments, with
stellar masses several times that of the Milky Way, yet their
star formation rates (SFRs) are comparable to or even lower than that of the Milky Way. In this paper, we investigate the molecular gas properties of such
galaxies to better understand the origin of their low SFRs. We present IRAM 30m CO observations of five extremely massive spirals from the CGM-MASS sample. We compare their
star formation efficiencies (SFEs) with the Kennicutt-Schmidt relation and find that these massive spirals generally exhibit low efficiency in converting molecular gas into
stars. We further compare their molecular gas masses with their atomic gas and
stellar masses, and also include the CHANG-ES sample
galaxies observed with the IRAM 30m
telescope in a similar manner for comparison. Our sample
galaxies show low efficiency in converting atomic to molecular gas and have lower molecular gas fractions, suggesting that their suppressed
star formation stems from both limited gas supply and inefficient
star formation. Considering potential cold gas sources in massive spirals, we argue that their current reservoirs likely originate from past starburst or merger events rather than ongoing
accretion in present isolated environments. Finally, we examine the location of these
galaxies on the baryonic Tully-Fisher relation, finding them
baryon-deficient and deviating from the trend of lower-mass
galaxies. This suggests either a significant undetected baryonic component or a flattening/turnover of the relation at the high-mass end, consistent with the
stellar mass-
halo mass relation.
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All authors Yu Huang, Jiangtao Li, Yan Jiang, Ping Zhou, Jianghui Xu, Liyuan Lu, Yang Yang
Cosmology and Nongalactic Astrophysics · Cross-listed from nucl-ex
Characterization of the ionization response of argon to nuclear recoils at the keV scale with the ReD experiment
P. Agnes, I. Ahmad, S. Albergo et al. (+42 more)
In the recent years, argon-based experiments looking for Dark Matter in the Universe have explored the non-standard scenario in which Dark Matter is made by low-mass Weakly Interacting Massive Particles, of mass in the range of 1-10 GeV instead of the canonical hundreds of GeV. Detecting such particles is challenging, as their expected signatures are
nuclear recoils with energies below 10 keV, observable solely via ionization. This necessitates a precise understanding of the detector response in this energy regime, which remains incomplete for argon. To address this, the ReD experiment was developed within the framework of the DarkSide-20k Collaboration to produce and characterize few-keV
nuclear recoils. A compact dual-phase argon Time Projection Chamber (TPC) was irradiated with
neutrons from a Cf252 source, to produce Ar
recoils in the energy range of interest via (n,n') elastic scattering. A downstream spectrometer composed of 18 plastic scintillators detected the
neutrons scattered off Ar
nuclei, enabling
recoil energy reconstruction via two-body kinematics. The ionization yield Qy of argon, defined as the number of electrons produced per unit energy deposit, was measured in a model-independent way between 2 and 10 keV. These measurements extend direct experimental coverage well below the previous limit of approximately 7 keV. The results are consistent with existing data above 7 keV, while they indicate a higher Qy at lower energies.
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All authors P. Agnes, I. Ahmad, S. Albergo, I. Albuquerque, M. Atzori Corona, M. Ave, B. Bottino, M. Cadeddu, A. Caminata, N. Canci, M. Caravati, L. Consiglio, S. Davini, L.K.S. Dias, G. Dolganov, G. Fiorillo, D. Franco, M. Gulino, T. Hessel, N. Kemmerich, M. Kimura, M. Kuzniak, M. La Commara, J. Machts, G. Matteucci, E. Moura Santos, E. Nikoloudaki, V. Oleynikov, L. Pandola, R. Perez Varona, N. Pino, S.M.R. Puglia, M. Rescigno, B. Sales Costa, S. Sanfilippo, A. Sung, C. Sunny, Y. Suvorov, R. Tartaglia, G. Testera, A. Tricomi, M. Wada, Y. Wang, R. Wojaczynski, P. Zakhary
High Energy Astrophysical Phenomena
Explodability matters: how realistic neutrino-driven explosions change explosive nucleosynthesis yields
Luca Boccioli and Lorenzo Roberti
Explosive nucleosynthesis is affected by many uncertainties, particularly regarding assumptions and prescriptions adopted during the
evolution of the
star. Moreover, simple explosion models are often used in the literature, which can introduce large errors in the assumed explosion energy and mass cut. In this paper, our goal is to analyze the explosion properties and nucleosynthesis of a large range of progenitors from three different
stellar evolution codes: FRANEC, KEPLER, and MESA. In particular, we will show the differences between the
neutrino-driven explosions simulated in this work with the much simpler bomb and piston models that are typically widely used in the literature. We will then focus on the impact of different explodabilities and different explosion dynamics on the nucleosynthetic yields. We adopt the
neutrino-driven core-collapse
supernova explosion code GR1D+, i.e. a spherically symmetric model with state-of-the-art microphysics and
neutrino transport and a time-dependent mixing-length model for
neutrino-driven convection. We carry out explosions up to several seconds after bounce, and then calculate the nucleosynthetic yields with the post-processing code SkyNet. We find that our 1D+ simulations yield explosion energies and remnant masses in agreement with observations of type II-P, IIb, and Ib
supernovae, as well as with the most recent 3D simulations of the explosion. We provide a complete set of yields for all the
stars simulated, including rotating, low-
metallicity, and binary progenitors. Finally, we find that piston and bomb models, compared to more realistic
neutrino-driven explosions, can artificially increase the production of Fe-peak elements, whereas the different explodability tends to cause discrepancies in the lighter elements.
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High Energy Astrophysical Phenomena
An Overview of Rossby Wave Instability in Accretion Discs surrounding Black Holes
Bibhuti Bhusan Dutta, Liza Devi, Biplob Sarkar et al. (+1 more)
The Rossby Wave Instability (RWI) has become an important concept in understanding the hydrodynamics (HDs) of
accretion discs (ADs), especially in systems around black holes (BHs) where
magnetic effects are either weak or absent. This instability is triggered by extrema (or sharp gradients) in the vortensity profile of the disc. Once activated, it leads to non-axisymmetric disturbances that can grow into large-scale
vortices. These
vortices play a significant role in the outward transport of angular momentum (AM). They may also help explain the presence of quasi-periodic oscillations (QPOs) observed in certain astrophysical systems such as X-ray binaries (XRBs). Here we review the main theoretical ideas behind RWI, as well as findings from more advanced three-dimensional (3D) and relativistic simulations. We also mention how the theory has been extended to include
magnetic fields and self-
gravity(SG) and what these results might imply for actual observations.
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All authors Bibhuti Bhusan Dutta, Liza Devi, Biplob Sarkar, Asish Jyoti Boruah
Astrophysics of Galaxies
Oxygen isotopes reveal low-mass star dominance in the Small Magellanic Cloud
Yan Gong, Zhi-yu Zhang, Christian Henkel et al. (+9 more)
Oxygen isotope abundances and their ratios are fingerprints of
stellar evolution and therefore provide a powerful tool in tracing the enrichment history of
galaxies. However, their behavior in low-
metallicity dwarf galaxies remains largely unexplored. The Small Magellanic Cloud (SMC), a nearby analog of young high-
redshift galaxies, offers an ideal laboratory to investigate this regime. Using the Atacama Compact Array, we observed the $J=2\to 1$ transitions of $^{12}$CO, $^{13}$CO, C$^{18}$O, and C$^{17}$O from the massive
star-forming region LIRS~36 (aka N12A), achieving the first detection of C$^{17}$O in the SMC. This detection enables the first direct measurement of the $^{18}$O/$^{17}$O abundance ratio of 0.87$\pm$0.26 in this
galaxy, substantially lower than all values in the literature, including molecular clouds in the Milky Way and other
galaxies. Such a low ratio of $^{18}$O/$^{17}$O, together with a high $^{13}$CO/C$^{18}$O ratio, indicates chemical enrichment dominated by low-mass
stars, consistent with the observed paucity of high-mass
stars in the SMC. We suggest that the SMC is governed by a top-light integrated
galaxy-wide initial mass function, predicted by the SMC's persistently low
star-formation activities.
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All authors Yan Gong, Zhi-yu Zhang, Christian Henkel, C.-H. Rosie Chen, Wenjin Yang, Xindi Tang, Leslie K. Hunt, Axel Weiss, Gang Wu, Yaoting Yan, Konstantin Grishunin, Karl M. Menten
High Energy Astrophysical Phenomena · Cross-listed from hep-ex
Investigating production of TeV-scale muons in extensive air shower at 2400 m underground
Xinshun Zhang, Shaomin Chen, Wei Dou et al. (+32 more)
Deep underground experiments present a new avenue to probe the first interactions in extensive air showers or hadronic interactions in the extreme forward phase space. The China Jinping Underground Laboratory, characterized by a vertical rock overburden of 2,400 m, provides an exceptionally effective shield against
cosmic muons with energies below 3 TeV. The surviving high-energy
muons, produced in the first interactions of extensive air showers, open a unique observational window into primary
cosmic rays from tens of TeV up to the PeV scale and beyond. This distinctive feature also enables detailed studies of charged
hadron production in the earliest stages of shower development. Using 1,338.6 live days of data collected with a one-ton prototype detector for the Jinping
Neutrino Experiment, we measured the underground
muon flux originating from air showers. The results show discrepancies of about 40% corresponding to significances of more than 2$\sigma$, relative to predictions from several leading hadronic interaction models. We interpret these findings from two complementary perspectives: (i) by adopting the expected
cosmic-ray spectra, we constrain the modeling of the first hadronic interactions in air showers and provide novel insights into resolving the long-standing
muon puzzle; and (ii) by assuming specific hadronic interaction models, we infer the mass composition of
cosmic rays, and our data favor a lighter component in the corresponding energy range. Our study demonstrates the potential of deep underground laboratories to provide new experimental insights into air shower physics and
cosmic rays.
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All authors Xinshun Zhang, Shaomin Chen, Wei Dou, Haoyang Fu, Guanghua Gong, Lei Guo, Ziyi Guo, XiangPan Ji, Jianmin Li, Jinjing Li, Bo Liang, Ye Liang, Qian Liu, Wentai Luo, Ming Qi, Wenhui Shao, Haozhe Sun, Jian Tang, Yuyi Wang, Zhe Wang, Changxu Wei, Jun Weng, Yiyang Wu, Benda Xu, Chuang Xu, Tong Xu, Tao Xue, Haoyan Yang, Yuzi Yang, Aiqiang Zhang, Bin Zhang, Yang Zhang, Zhicai Zhang, Lin Zhao, Yangheng Zheng
High Energy Astrophysical Phenomena
A Practical Framework for Estimating the Repetition Likelihood of Fast Radio Bursts from Spectral Morphology
Wan-Peng Sun, Yong-Kun Zhang, Ji-Guo Zhang et al. (+6 more)
The repeating behavior of fast
radio bursts (FRBs) is regarded as a key clue to understanding their physical origin, yet reliably distinguishing repeaters from apparent non-repeaters with current observations remains challenging. Here we propose a physically interpretable and practically quantifiable classification framework based on spectral morphology. Using dimensionality reduction, clustering, and feature-importance analysis, we identify the spectral running $r$ and spectral index $\gamma$ as the most critical parameters for distinguishing repeaters from apparent non-repeaters in the CHIME/FRB sample. In the $\gamma$-$r$ space, repeaters preferentially occupy regions with steeper, narrower-band spectra, whereas non-repeaters cluster in flatter, broader-band regions, resulting in a clear density separation. We further construct an empirical probability map in the $\gamma$-$r$ space, showing a clear gradient of repetition likelihood, from $\sim 65\%$ in the high-repetition region to $\sim 5\%$ in the low-repetition region. Combining this with Gaussian Mixture Model posterior analysis, we identify several apparent non-repeaters with high inferred repetition probability, recommending them as priority targets for future monitoring. This framework provides a simple and generalizable tool for assessing repeatability in the CHIME/FRB sample and highlights the diagnostic power of spectral morphology in unveiling FRB origins.
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All authors Wan-Peng Sun, Yong-Kun Zhang, Ji-Guo Zhang, Xiaohui Liu, Yichao Li, Fu-Wen Zhang, Wan-Ting Hou, Jing-Fei Zhang, Xin Zhang
High Energy Astrophysical Phenomena
The metallicity dependence of long-duration gamma-ray bursts
Paul Disberg, Anne Lankreijer, Martyna Chruślińska et al. (+5 more)
Both theoretical models and observations of collapsar created gamma-ray bursts – typically long-duration gamma-ray bursts (LGRBs) – suggest that these transients cannot occur at high
metallicity, likely due to angular momentum losses via
stellar winds for potential progenitor
stars. However, the precise
metallicity threshold (if it is a hard threshold) above which the formation of LGRBs is suppressed is still a topic of discussion. We investigated observed LGRBs and the properties of their host
galaxies to constrain this
metallicity dependence. In order to compute LGRB rates we modelled the
cosmic history of
star formation, as a function of host
galaxy metallicity and
stellar mass, and added a LGRB efficiency function that can include various shapes including abrupt cutoffs and more gradual variations in the GRB yield with
metallicity. In contrast to previous work, this model includes scatters in the relations between mass,
metallicity, and
star formation rate, as well as a scatter in the
metallicity distribution inside
galaxies. We then varied both the threshold value and shape, and compared it to observed LGRBs and the properties of their host
galaxies. In our model a sharp cutoff at an oxygen abundance $Z_{\text{O/H}}=12+\log(\text{O/H})=8.6\pm0.1$ (corresponding to $\sim0.6Z_{\odot}$) provides the best explanation for the observed LGRB data. In contrast, a lower threshold proposed in literature (i.e. at $Z_{\text{O/H}}=8.3$ or $\sim0.3Z_{\odot}$) fits observations poorly. We therefore conclude that, in contrast to most theoretical LGRB models, a relatively high
metallicity threshold at near-
solar values provides the best match between our model and observed LGRBs.
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All authors Paul Disberg, Anne Lankreijer, Martyna Chruślińska, Andrew J. Levan, Gijs Nelemans, Nial R. Tanvir, Charlotte R. Angus, Ilya Mandel
Cosmology and Nongalactic Astrophysics
XRISM-Subaru views of Abell 754: an off-axis, near-line-of-sight merging cluster
Nobuhiro Okabe, Yuki Omiya, Kazuhiro Nakazawa et al. (+4 more)
We report a weak-
lensing (WL) mass measurement for the merging cluster Abell 754 and impose constraints on the merger trajectory. The trajectory analysis adopts a two-body model with a point-mass approximation and dynamical friction, refined using numerical simulations of major mergers and characterized by Euler angles. We first conduct WL analysis using the two-dimensional shear pattern from the Subaru HSC in combination with Suprime-Cam images to assist in color selection. The WL mass map shows a distinct double-peak structure located around the western and eastern brightest cluster
galaxies as reported in the literature. The two-
halo component analysis, which utilizes the 2D shear pattern over the cluster entire region and considers the
lensing covariance
matrix from uncorrelated large-scale structures, indicates mass values of $M_{200}^W=3.13_{-1.00}^{+1.53}\times10^{14}h_{70}^{-1}M_\odot$ and $M_{200}^E=6.41_{-1.97}^{+2.92}\times10^{14}h_{70}^{-1}M_\odot$. Thus, the eastern mass component associated with the X-ray tadpole-shaped gas is the main cluster. No substantial structural components are detected in the line-of-sight velocities of the member
galaxies. Utilizing WL parameters, line-of-sight velocities, and X-ray information on morphology and kinematics, we determine an impact parameter of approximately 0.77 Mpc at an initial separation of 2 Mpc from the main cluster. The merger plane is inclined at about 20 degrees relative to the line-of-sight. Interestingly, this system is an off-axis, near-line-of-sight merger. This characteristic arises because the trajectory within the merger plane is altered during the pericenter passage, causing the apparent motion to transition from predominantly along the line-of-sight before the core passage to mainly within the plane of the sky afterward. This study will assist in conducting numerical simulations to understand the XRISM observations.
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All authors Nobuhiro Okabe, Yuki Omiya, Kazuhiro Nakazawa, Naomi Ota, Nhan T. Nguyen-Dang, Yuto Ichinohe, Shutaro Ueda
Solar and Stellar Astrophysics
Multiwavelength spectroscopic observations of a quiescent prominence
Jianchao Xue, Ping Zhang, Jean-Claude Vial et al. (+5 more)
In this paper we focus on the analysis of the multiwavelength spectroscopic observations of a quiescent prominence. The spectral and geometrical parameters in the prominence were derived and used to constrain the NLTE radiative transfer models. Applying this method with multiwavelength observations provides a good opportunity to reduce the large range of thermodynamic parameters in
solar prominences. We used time-slice and optical flow methods in order to derive the plane-of-sky (POS) velocities, and used
gravity center and peak position methods on Mg II h&k and H I Ly-alpha profiles to compute the line-of-sight (LOS) velocities. We used the integrated intensities and FWHM values of the H-alpha, Ca II H, and Mg II h&k lines to compare with the NLTE radiative transfer computations. Ionization degree and thickness of the prominence
plasma could be further derived. Opposite flows are observed along two strands between prominence barbs. The POS velocity can reach 20 km/s and the largest LOS velocity is > 90 km/s. The derived electron densities range from 6.5e9 cm-3 to 2.7e10 cm-3, and the derived total hydrogen densities range from 7.4e9 cm-3 to 6.6e10 cm-3. The temperature ranges from 7 000 to 14 000 K. The ionization degree of hydrogen is in the range of 0.40 to 0.91. The comparison between averaged and modeled profiles of Mg II and Ly-alpha lines shows that macro-velocities of 15 km/s and 20 km/s are required, respectively. The bulk motions among prominence barbs indicate that the prominence
plasma is not confined within
magnetic dips but exhibits a large-scale behavior. The presence of high-speed cool
plasma flows, along with a wide range of
plasma densities and temperatures, suggests that the prominence
plasma is far from thermodynamic
equilibrium and is inherently dynamic in nature.
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All authors Jianchao Xue, Ping Zhang, Jean-Claude Vial, Li Feng, Maciej Zapiór, Werner Curdt, Hui Li, Weiqun Gan
Solar and Stellar Astrophysics
Distinct barium isotope ratios in CEMP-s and CEMP-rs stars
T.M. Sitnova, L.I. Mashonkina, A.M. Romanovskaya et al. (+2 more)
We present a spectroscopic analysis of ten carbon enhanced metal-poor (CEMP)
stars of type CEMP-s and CEMP-rs and determine their NLTE abundances of Ba and Eu, as well as the fractions of the odd Ba isotopes (F_odd). The Ba abundances inferred from the resonance Ba II 4554 and 4934 A lines depend on the adopted Ba isotope mixture. We perform calculations for different F_odd from 0.1 to 1.0 and determine the corresponding abundances from the Ba II resonance lines in each sample
star. In addition, we determine the Ba abundances from the Ba II subordinate lines, which are almost independent of F_odd. We then compare the Ba abundances derived from the subordinate lines with those from the Ba II resonance lines. We found different F_odd values in CEMP-s and CEMP-rs
stars. CEMP-s
stars exhibit F_odd = 0.05$_{-0.03}^{+0.07}$, 0.17$_{-0.14}^{+0.63}$, 0.19$_{-0.14}^{+0.50}$, and 0.19$_{-0.12}^{+0.33}$. The obtained values agree, within the error bars, with the s-process F_odd = 0.10 and the
solar F_odd = 0.18. Although the uncertainties are large, in three of four
stars, the possibility of Ba isotopes origin in a pure r-process with F_odd = 0.75 can be excluded. CEMP-rs
stars show F_odd = 0.34$_{-0.21}^{+0.55}$, 0.36$_{-0.14}^{+0.23}$, 0.44$_{-0.22}^{+0.43}$, 0.53$_{-0.38}^{+0.47}$, and 0.57$_{-0.31}^{+0.43}$, which are higher compared to those in CEMP-s
stars. Although the uncertainties are large, in four of five
stars, the possibility of a pure s-process origin for the Ba isotopes can be excluded. The obtained values agree, within the error bars, with the predicted i-process F_odd = 0.6 to 0.8. Our analysis of CEMP-rs
stars with [Ba/Eu] > 0 argues that their [Ba/Eu] and F_odd cannot be jointly explained by a mixture of material produced by the r- and s-processes. The obtained results argue that the i-process is responsible for the chemical composition of these CEMP-rs
stars.
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All authors T.M. Sitnova, L.I. Mashonkina, A.M. Romanovskaya, R.E. Giribaldi, A. Choplin